linux-kernel - Re: [PATCH 0/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning

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Message-ID: <20110622004608.GS25383@sequoia.sous-sol.org>
Date:	Tue, 21 Jun 2011 17:46:08 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Nai Xia <nai.xia@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Izik Eidus <izik.eidus@...ellosystems.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Rik van Riel <riel@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2 V2] ksm: take dirty bit as reference to avoid
 volatile pages scanning

* Nai Xia (nai.xia@...il.com) wrote:
> Compared to the first version, this patch set addresses the problem of
> dirty bit updating of virtual machines, by adding two mmu_notifier interfaces.
> So it can now track the volatile working set inside KVM guest OS.
> 
> V1 log:
> Currently, ksm uses page checksum to detect volatile pages. Izik Eidus 
> suggested that we could use pte dirty bit to optimize. This patch series
> adds this new logic.
> 
> Preliminary benchmarks show that the scan speed is improved by up to 16 
> times on volatile transparent huge pages and up to 8 times on volatile 
> regular pages.

Did you run this only in the host (which would not trigger the notifiers
to kvm), or also run your test program in a guest?

thanks,
-chris
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